In biochemistry, the term “macromolecules” is applied to molecules of large molecular mass and broadly includes biopolymers such as nucleic acids, proteins, and carbohydrates as well as non-polymeric molecules such as lipids and macrocycles.
Macromolecular assemblies (MMAs) are massive chemical structures (typically hundreds of kDa or even several MDa) and encompass large biological molecules such as viruses, protein complexes, protein-ligand complexes, protein-DNA complexes, antibody receptors and other complex mixtures of polypeptides, polysaccharides and so forth, and also non-biological materials such as nanoparticles.
Herein the term macromolecular assemblies (MMAs) will be used to refer to both macromolecules and macromolecular assemblies.
Macromolecular assemblies are defined both by their compositional structure and also by their chemical shape. The 3D shape (conformation) of the MMA is often of a great interest because, for example, knowledge of the shape of an MMA can help in the understanding of how that MMA interacts with other molecules. Applications of structural and dynamic MMA analyses range from the detailed study of equilibria and dynamic interconversions between different MMA structures as influenced by environmental changes or binding of substrates or cofactors, to the analysis of intact nano-machineries such as whole virus particles, organelles, proteasomes and ribosomes.
Generally, 3D structural information is not widely available even for many known proteins or protein complexes, therefore the problem of determining the structure of MMAs is still acute.
Various methods and techniques for experimentally investigating MMA structure exist. An introductory review of these is given in “From words to literature in structural proteomics”, by Sali et al, Nature 422, 216-225, 13 Mar. 2003. Techniques such as x-ray crystallography, nuclear magnetic resonance, 2 dimensional electron microscopy, cryoelectron tomography, and many others each provide different perspectives on the 3D shape of MMAs. Each in turn has advantages and disadvantages over other techniques.
The present invention proposes an alternative approach to that described in the art, for the determination of the structure of an MMA.